Using an AngularJS timeout - angularjs

Question

I'm new to AngularJS. I'm currently looking at the $timeout service. I understand that it's like a wrapper for the setTimeout function. The documentation says that it provides exception handling. In addition, the documentation says I can cancel and flush a timeout.
Can someone please explain to me when an exception would happen with a timeout? I also don't understand why I need to flush a timeout. I would love an explanation or maybe a jsfiddle. For the life of me, I can't figure out why or even how to use these additional features.
Update:
When I attempt to run the stop function, the catch handler associated with myTimer get's thrown. Here is my code:
var myTimer = null;
$scope.hasStarted = false;
$scope.start = function () {
if ($scope.hasStarted === false) {
$scope.isTimerActive = true;
myTimer = $timeout(function () { $scope.isTimerActive = false; }, 5000);
myTimer.catch(function (err) {
alert("An error happened with the clock.");
});
}
}
$scope.stopClock = function () {
$timeout.cancel(myTimer);
$scope.isClockActive = false;
}
Thank you!

Answer 1

$timeout is most awesome indeed.
Exception handling
$timeout returns a promise which can have an error state. For example
var timePromise = $timeout(function(){
throw new Error('I messed up');
}, 10000);
timePromise.catch(function(err){
// do something with the error
});
read all about promises here.
Cancel
Canceling a $timeout is easy. Instead of using clearTimeout you pass the promise back.
var timePromise = $timeout(function(){
// do thing
}, 23432);
// wait I didn't mean it!
$timeout.cancel(timePromise);
Flush
Flush is most useful for unit testing, ultimately it fires any outstanding callbacks.
$timeout(function(){
console.log('$timeout flush');
}, 222);
$timeout(function(){
console.log('rocks my face');
}, 234232);
$timeout.flush(); // both console logs will fire right away!
or this file:
var itsDone = false;
$timeout(function(){
itsDone = true;
}, 5000);
with this test:
// old no flush way (async)
it('should be done', function(done){
expect(isDone).to.be.false;
setTimeout(function(){
expect(isDone).to.be.true;
done();
}, 5001);
});
// now with flush
it('should be done', function(){
expect(isDone).to.be.false;
$timeout.flush();
expect(isDone).to.be.true;
});